The ketogenic diet in a pill: is this possible?

Using Dictyostelium to Advance Our Understanding of the Role of Medium Chain Fatty Acids in Health and Disease

Ketogenic diets have been utilized for many years to improve health, and as a dietary approach for the treatment of a range of diseases, where the mechanism of these low carbohydrate and high fat diets is widely considered to be through the production of metabolic products of fat breakdown, called ketones. One of these diets, the medium chain triglyceride ketogenic diet, involves high fat dietary intake in the form of medium chain fatty acids (MCFAs), decanoic and octanoic acid, and is commonly used in endurance and high intensity exercises but has also demonstrated beneficial effects in the treatment of numerous pathologies including drug resistant epilepsy, cancer, and diabetes. Recent advances, using Dictyostelium discoideum as a model, have controversially proposed several direct molecular mechanisms for decanoic acid in this diet, independent of ketone generation. Studies in this model have identified that decanoic acid reduces phosphoinositide turnover, diacylglycerol kinase (DGK) activity, and also inhibits the mechanistic target of rapamycin complex 1 (mTORC1). These discoveries could potentially impact the treatment of a range of disorders including epilepsy, cancer and bipolar disorder. In this review, we summarize the newly proposed mechanisms for decanoic acid, identified using D. discoideum, and highlight potential roles in health and disease treatment.

Ketonuria and Seizure Control in the Medium Chain Triglyceride and Classic Ketogenic Diets

We hypothesized that children receiving medium-chain triglyceride ketogenic diet (MCTKD) experience similar seizure reduction despite lower ketosis compared with classic ketogenic diet (CKD). Children initiating CKD or MCTKD were enrolled in a prospective observational study. Forty-five children completed 6 months of KD (n = 17 MCTKD, n = 28 CKD). The proportion achieving ≥50% seizure reduction was 71% CKD group and 59% MCTKD group; ≥90% reduction was 32% and 36% in CKD and MCTKD groups, respectively. CKD had higher urine ketones (≥8 mmol/L: 79% vs. 36%, p = 0.005). Children receiving MCTKD experience similar seizure control to CKD despite lower urine ketone measures.

The ketogenic diet raises brain oxygen levels, attenuates postictal hypoxia, and protects against learning impairments

OBJECTIVES

A prolonged vasoconstriction/hypoperfusion/hypoxic event follows self-terminating focal seizures. The ketogenic diet (KD) has demonstrated efficacy as a metabolic treatment for intractable epilepsy and other disorders but its effect on local brain oxygen levels is completely unknown. This study investigated the effects of the KD on tissue oxygenation in the hippocampus before and after electrically elicited (kindled) seizures and whether it could protect against a seizure-induced learning impairment. We also examined the effects of the ketone β-hydroxybutyrate (BHB) as a potential underlying mechanism.

METHODS

Male and female rats were given access to one of three diet protocols 2 weeks prior to the initiation of seizures: KD, caloric restricted standard chow, and ad libitum standard chow. Dorsal hippocampal oxygen levels were measured prior to initiation of diets as well as before and after a 10-day kindling paradigm. Male rats were then tested on a novel object recognition task to assess postictal learning impairments. In a separate cohort, BHB was administered 30 min prior to seizure elicitation to determine whether it influenced oxygen dynamics.

RESULTS

The KD increased dorsal hippocampal oxygen levels, ameliorated postictal hypoxia, and prevented postictal learning impairments. Acute BHB administration did not alter oxygen levels before or after seizures.

INTERPRETATION

The ketogenic diet raised brain oxygen levels and attenuated severe postictal hypoxia likely through a mechanism independent of ketosis and shows promise as a non-pharmacological treatment to prevent the postictal state.

Expression Pattern of ALOXE3 in Mouse Brain Suggests Its Relationship with Seizure Susceptibility

Arachidonic acid (AA), a polyunsaturated fatty acid, is involved in the modulation of neuronal excitability in the brain. Arachidonate lipoxygenase 3 (ALOXE3), a critical enzyme in the AA metabolic pathway, catalyzes the derivate of AA into hepoxilins. However, the expression pattern of ALOXE3 and its role in the brain has not been described until now. Here we showed that the levels of Aloxe3 mRNA and protein kept increasing since birth and reached the highest level at postnatal day 30 in the mouse hippocampus and temporal cortex. Histomorphological analyses indicated that ALOXE3 was enriched in adult hippocampus, somatosensory cortex and striatum. The distribution was restricted to the neurites of function-specific subregions, such as mossy fibre connecting hilus and CA3 neurons, termini of Schaffer collateral projections, and the layers III and IV of somatosensory cortex. The spatiotemporal expression pattern of ALOXE3 suggests its potential role in the modulation of neural excitability and seizure susceptibility. In fact, decreased expression of ALOXE3 and elevated concentration of AA in the hippocampus was found after status epilepticus (SE) induced by pilocarpine. Local overexpression of ALOXE3 via adeno-associated virus gene transfer restored the elevated AA level induced by SE, alleviated seizure severities by increasing the latencies to myclonic switch, clonic convulsions and tonic hindlimb extensions, and decreased the mortality rate in the pilocarpine-induced SE model. These results suggest that the expression of ALOXE3 is a crucial regulator of AA metabolism in brain, and potentially acts as a regulator of neural excitability, thereby controlling brain development and seizure susceptibility.

Efficacy of medium chain triglyceride oil dietary supplementation in reducing seizure frequency in dogs with idiopathic epilepsy without cluster seizures: a non-blinded, prospective clinical trial

BACKGROUND

Despite appropriate antiseizure drug (ASD) treatment, around two-thirds of dogs with idiopathic epilepsy (IE) have seizures long-term and 20-30per cent of affected dogs remain poorly controlled.

METHODS

The current study aim is to test in a field trial the efficacy and tolerability of a commercially available diet enriched with 6.5per cent medium chain triglyceride (MCT) oil in dogs (n=21) with at least a tier 1 idiopathic epilepsy diagnosis, without cluster seizures, in 10 veterinary practices across Europe. Each dog's quality of life (QoL), ataxia, sedation and frequency and severity of seizures were recorded by owners throughout the study.

RESULTS

The mean seizure frequency per month, averaged over the entire 84-day study, significantly (P=0.04) decreased 32per cent compared with the baseline monthly seizure frequency recorded during the month immediately before feeding the diet. Similarly, the seizure days rate (days/month) also declined (P<0.001) by 42per cent. QoL was reported as very good to excellent (>8.5/10) in 20 of the 21 dogs before starting the diet and this remained unchanged during the trial.

CONCLUSIONS

This study demonstrates the use of a diet enriched with MCTs as an adjunct to ASD treatment may have some antiseizure properties for dogs diagnosed with IE, as demonstrated in previous studies.

Ketogenic Dietary Therapy Controversies for Its Second Century

As the ketogenic diet approaches 100 years of continuous use, we reflect on its successes and consider new avenues of research for the next century. One controversial question is regarding whether ketogenic dietary therapies could be successful first-line treatments for epilepsy. Second, is it possible to mimic the mechanisms of action of ketogenic dietary therapy with a drug (eg, a tablet formulation)? A third controversy worthy of future study involves its expanded usage in adults with refractory epilepsy and its role in treating women of childbearing age. Finally, as flexible, alternative diets have recently become widely available, is it feasible and safe to have families and patients start ketogenic dietary therapy successfully on their own with limited medical supervision?

Ketone Administration for Seizure Disorders: History and Rationale for Ketone Esters and Metabolic Alternatives

The ketogenic diet (KD) is a high-fat, low-carbohydrate treatment for medically intractable epilepsy. One of the hallmark features of the KD is the production of ketone bodies which have long been believed, but not yet proven, to exert direct anti-seizure effects. The prevailing view has been that ketosis is an epiphenomenon during KD treatment, mostly due to clinical observations that blood ketone levels do not correlate well with seizure control. Nevertheless, there is increasing experimental evidence that ketone bodies alone can exert anti-seizure properties through a multiplicity of mechanisms, including but not limited to: (1) activation of inhibitory adenosine and ATP-sensitive potassium channels; (2) enhancement of mitochondrial function and reduction in oxidative stress; (3) attenuation of excitatory neurotransmission; and (4) enhancement of central γ-aminobutyric acid (GABA) synthesis. Other novel actions more recently reported include inhibition of inflammasome assembly and activation of peripheral immune cells, and epigenetic effects by decreasing the activity of histone deacetylases (HDACs). Collectively, the preclinical evidence to date suggests that ketone administration alone might afford anti-seizure benefits for patients with epilepsy. There are, however, pragmatic challenges in administering ketone bodies in humans, but prior concerns may largely be mitigated through the use of ketone esters or balanced ketone electrolyte formulations that can be given orally and induce elevated and sustained hyperketonemia to achieve therapeutic effects.

2-Deoxyglucose and Beta-Hydroxybutyrate: Metabolic Agents for Seizure Control

Current anti-seizure drugs (ASDs) are believed to reduce neuronal excitability through modulation of ion channels and transporters that regulate excitability at the synaptic level. While most patients with epilepsy respond to ASDs, many remain refractory to medical treatment but respond favorably to a high-fat, low-carbohydrate metabolism-based therapy known as the ketogenic diet (KD). The clinical effectiveness of the KD has increasingly underscored the thesis that metabolic factors also play a crucial role in the dampening neuronal hyperexcitability that is a hallmark feature of epilepsy. This notion is further amplified by the clinical utility of other related metabolism-based diets such as the modified Atkins diet and the low-glycemic index treatment (LGIT). Traditional high-fat diets are characterized by enhanced fatty acid oxidation (which produces ketone bodies such as beta-hydroxybutyrate) and a reduction in glycolytic flux, whereas the LGIT is predicated mainly on the latter observation of reduced blood glucose levels. As dietary implementation is not without challenges regarding clinical administration and patient compliance, there is an inherent desire and need to determine whether specific metabolic substrates and/or enzymes might afford similar clinical benefits, hence validating the concept of a “diet in a pill.” Here, we discuss the evidence for one glycolytic inhibitor, 2-deoxyglucose (2DG) and one metabolic substrate, β-hydroxybutyrate (BHB) exerting direct effects on neuronal excitability, highlight their mechanistic differences, and provide the strengthening scientific rationale for their individual or possibly combined use in the clinical arena of seizure management.

Modified ketogenic diets in adults with refractory epilepsy: Efficacious improvements in seizure frequency, seizure severity, and quality of life

OBJECTIVE

This study evaluates the efficacy of a modified ketogenic diet (MKD) on seizure frequency, severity, and quality of life (QOL), as well as potential complications of MKD therapy among adults with drug-resistant epilepsy (DRE).

METHODS

Changes in seizure frequency, severity, QOL, and side effects were retrospectively examined among adults, ≥17 years of age, with DRE (≥2 antiepileptic drugs [AEDs]), after 3 months of MKD therapy. Attention was paid to medication or vagus nerve stimulator (VNS) changes as well to evaluate potential confounders.

RESULTS

A total of 60% (n = 33) of the 55 individuals reported ≥50% seizure frequency improvement, 42 (76%) reported improvement in seizure severity, and 48 (87%) reported improvement in QOL. More patients following a modified ketogenic diet - 15 g net carbohydrate daily (MKD-15) (95%) compared with a MKD-50 (69%) reported improvement in QOL (p = 0.02). Weight among the entire sample declined from 77.5 (20) kg to 73.9 (19.0) kg (p < 0.0001), and total cholesterol (TC), low density lipoprotein (LDL), and total cholesterol:high density lipoprotein (TC:HDL) increased significantly (p = 0.03, p = 0.04, and p = 0.02, respectively). Free carnitine values were available for a select number of patients, 26 (47%) at baseline, and 7 (13%) at follow-up, of which 8 (31%) at baseline, and 2 (29%) at follow-up had carnitine deficiency (<25 nmol/mL). Constipation was noted in 5 patients (9%), and no kidney stones were reported during the study period. There were no statistical differences in number or dose changes for AED or VNS during the study period.

SIGNIFICANCE

Modified ketogenic diet therapies reduce seizure frequency and severity and improve QOL among adults with DRE with few side effects outside of weight loss, a desired outcome among many adults with DRE. More restrictive MKDs may offer improved seizure severity and QOL. Modified ketogenic diet therapy increases LDL cholesterol, which may be cardioprotective if related to an increase in LDL particle size with high saturated fat intake; however, more research is needed examining LDL particle size changes among those receiving MKD therapy.

Delaying latency to hyperbaric oxygen-induced CNS oxygen toxicity seizures by combinations of exogenous ketone supplements

Central nervous system oxygen toxicity (CNS-OT) manifests as tonic-clonic seizures and is a limitation of hyperbaric oxygen therapy (HBOT), as well as of recreational and technical diving associated with elevated partial pressure of oxygen. A previous study showed that ketone ester (1,3-butanediol acetoacetate diester, KE) administration delayed latency to seizures (LS) in 3-month-old Sprague-Dawley (SD) rats. This study explores the effect of exogenous ketone supplements in additional dosages and formulations on CNS-OT seizures in 18 months old SD rats, an age group correlating to human middle age. Ketogenic agents were given orally 60 min prior to exposure to hyperbaric oxygen and included control (water), KE (10 g/kg), KE/2 (KE 5 g/kg + water 5 g/kg), KE + medium-chain triglycerides (KE 5 g/kg + MCT 5 g/kg), and ketone salt (Na+ /K+ βHB, KS) + MCT (KS 5 g/kg + MCT 5 g/kg). Rats were exposed to 100% oxygen at 5 atmospheres absolute (ATA). Upon seizure presentation (tonic-clonic movements) experiments were immediately terminated and blood was tested for glucose and D-beta-hydroxybutyrate (D-βHB) levels. While blood D-βHB levels were significantly elevated post-dive in all treatment groups, LS was significantly delayed only in KE (P = 0.0003), KE/2 (P = 0.023), and KE + MCT (P = 0.028) groups. In these groups, the severity of seizures appeared to be reduced, although these changes were significant only in KE-treated animals (P = 0.015). Acetoacetate (AcAc) levels were also significantly elevated in KE-treated animals. The LS in 18-month-old rats was delayed by 179% in KE, 219% in KE + MCT, and 55% in KE/2 groups, while only by 29% in KS + MCT. In conclusion, KE supplementation given alone and in combination with MCT elevated both βHB and AcAc, and delayed CNS-OT seizures.

Impact of Dietary Fats on Brain Functions

BACKGROUND

Adequate dietary intake and nutritional status have important effects on brain functions and on brain health. Energy intake and specific nutrients excess or deficiency from diet differently affect cognitive processes, emotions, behaviour, neuroendocrine functions and synaptic plasticity with possible protective or detrimental effects on neuronal physiology. Lipids, in particular, play structural and functional roles in neurons. Here the importance of dietary fats and the need to understand the brain mechanisms activated by peripheral and central metabolic sensors. Thus, the manipulation of lifestyle factors such as dietary interventions may represent a successful therapeutic approach to maintain and preserve brain health along lifespan.

METHODS

This review aims at summarizing the impact of dietary fats on brain functions.

RESULTS

Starting from fat consumption, nutrient sensing and food-related reward, the impact of gut-brain communications will be discussed in brain health and disease. A specific focus will be on the impact of fats on the molecular pathways within the hypothalamus involved in the control of reproduction via the expression and the release of Gonadotropin-Releasing Hormone. Lastly, the effects of specific lipid classes such as polyunsaturated fatty acids and of the "fattest" of all diets, commonly known as "ketogenic diets", on brain functions will also be discussed.

CONCLUSION

Despite the knowledge of the molecular mechanisms is still a work in progress, the clinical relevance of the manipulation of dietary fats is well acknowledged and such manipulations are in fact currently in use for the treatment of brain diseases.

Optimal clinical management of children receiving dietary therapies for epilepsy: Updated recommendations of the International Ketogenic Diet Study Group

Ketogenic dietary therapies (KDTs) are established, effective nonpharmacologic treatments for intractable childhood epilepsy. For many years KDTs were implemented differently throughout the world due to lack of consistent protocols. In 2009, an expert consensus guideline for the management of children on KDT was published, focusing on topics of patient selection, pre‐KDT counseling and evaluation, diet choice and attributes, implementation, supplementation, follow‐up, side events, and KDT discontinuation. It has been helpful in outlining a state‐of‐the‐art protocol, standardizing KDT for multicenter clinical trials, and identifying areas of controversy and uncertainty for future research. Now one decade later, the organizers and authors of this guideline present a revised version with additional authors, in order to include recent research, especially regarding other dietary treatments, clarifying indications for use, side effects during initiation and ongoing use, value of supplements, and methods of KDT discontinuation. In addition, authors completed a survey of their institution's practices, which was compared to responses from the original consensus survey, to show trends in management over the last 10 years.

Metabolomics As a Tool for the Characterization of Drug-Resistant Epilepsy

Purpose

Drug resistance is a critical issue in the treatment of epilepsy, contributing to clinical emergencies and increasing both serious social and economic burdens on the health system. The wide variety of potential drug combinations followed by often failed consecutive attempts to match drugs to an individual patient may mean that this treatment stage may last for years with suboptimal benefit to the patient. Given these challenges, it is valuable to explore the availability of new methodologies able to shorten the period of determining a rationale pharmacologic treatment. Metabolomics could provide such a tool to investigate possible markers of drug resistance in subjects with epilepsy.

Methods

Blood samples were collected from (1) controls (C) (n = 35), (2) patients with epilepsy “responder” (R) (n = 18), and (3) patients with epilepsy “non-responder” (NR) (n = 17) to the drug therapy. The samples were analyzed using nuclear magnetic resonance spectroscopy, followed by multivariate statistical analysis.

Key findings

A different metabolic profile based on metabolomics analysis of the serum was observed between C and patients with epilepsy and also between R and NR patients. It was possible to identify the discriminant metabolites for the three classes under investigation. Serum from patients with epilepsy were characterized by increased levels of 3-OH-butyrate, 2-OH-valerate, 2-OH-butyrate, acetoacetate, acetone, acetate, choline, alanine, glutamate, scyllo-inositol (C < R < NR), and decreased concentration of glucose, lactate, and citrate compared to C (C > R > NR).

Significance

In conclusion, metabolomics may represent an important tool for discovery of differences between subjects affected by epilepsy responding or resistant to therapies and for the study of its pathophysiology, optimizing the therapeutic resources and the quality of life of patients.

A ketogenic diet accelerates neurodegeneration in mice with induced mitochondrial DNA toxicity in the forebrain

Mitochondrial genome maintenance plays a central role in preserving brain health. We previously demonstrated accumulation of mitochondrial DNA damage and severe neurodegeneration in transgenic mice inducibly expressing a mutated mitochondrial DNA repair enzyme (mutUNG1) selectively in forebrain neurons. Here, we examine whether severe neurodegeneration in mutUNG1-expressing mice could be rescued by feeding the mice a ketogenic diet, which is known to have beneficial effects in several neurological disorders. The diet increased the levels of superoxide dismutase 2, and mitochondrial mass, enzymes, and regulators such as SIRT1 and FIS1, and appeared to downregulate N-methyl-D-aspartic acid (NMDA) receptor subunits NR2A/B and upregulate γ-aminobutyric acid A (GABA_A) receptor subunits α₁. However, unexpectedly, the ketogenic diet aggravated neurodegeneration and mitochondrial deterioration. Electron microscopy showed structurally impaired mitochondria accumulating in neuronal perikarya. We propose that aggravation is caused by increased mitochondrial biogenesis of generally dysfunctional mitochondria. This study thereby questions the dogma that a ketogenic diet is unambiguously beneficial in mitochondrial disorders.

A prospective study on changes in blood levels of cholecystokinin-8 and leptin in patients with refractory epilepsy treated with the ketogenic diet

OBJECTIVE

To evaluate the changes in serum CCK-8 and leptin levels in patients with refractory epilepsy treated with the ketogenic diet (KD).

METHODS

In this prospective study, patients aged between one and 40 years with refractory epilepsy were included. CCK-8 and leptin were measured in serum at baseline and after three and 12 months of treatment with the KD using an enzyme-linked Immunoabsorbant Assay. Seizure frequency and responsiveness were calculated.

RESULTS

Fifty-four patients were included; 26 patients (48%) were still on the KD at 12 months. After three and 12 months, respectively, 39% and 26% were responders. CCK-8 values were statistically significantly increased at three months (p=0.005) and 12 months (p=0.012). In responders, at three months follow-up, this increase of CCK-8 was significant (p=0.020), whereas in the non-responders it was not (p=0.34). Leptin values were decreased at three and 12 months, the decrease at three months being statistically significant in post-pubertal men (p=0.028) and post-pubertal women (p=0.007).

SIGNIFICANCE

In responders to the KD, serum CCK-8 increased statistically significantly during treatment at three months. Serum leptin decreased statistically significantly at three months in men and in post-pubertal women. It is plausible that the increase of CCK-8 and the decrease of leptin contribute to the anti-convulsive effect of the KD.

Ketone Bodies Mediate Antiseizure Effects

Investigators from The Barrow Neurological Institute, Creighton University, University of Kentucky and the University of Calgary Faculty of Medicine investigated the effect of ketone bodies and the ketogenic diet on epileptic Kcna1-null mice.

Ketogenic diet restores aberrant cortical motor maps and excitation-to-inhibition imbalance in the BTBR mouse model of autism spectrum disorder

Autism spectrum disorder (ASD) is an increasingly prevalent neurodevelopmental disorder characterized by deficits in sociability and communication, and restricted and/or repetitive motor behaviors. Amongst the diverse hypotheses regarding the pathophysiology of ASD, one possibility is that there is increased neuronal excitation, leading to alterations in sensory processing, functional integration and behavior. Meanwhile, the high-fat, low-carbohydrate ketogenic diet (KD), traditionally used in the treatment of medically intractable epilepsy, has already been shown to reduce autistic behaviors in both humans and in rodent models of ASD. While the mechanisms underlying these effects remain unclear, we hypothesized that this dietary approach might shift the balance of excitation and inhibition towards more normal levels of inhibition. Using high-resolution intracortical microstimulation, we investigated basal sensorimotor excitation/inhibition in the BTBR T+Itpr(tf)/J (BTBR) mouse model of ASD and tested whether the KD restores the balance of excitation/inhibition. We found that BTBR mice had lower movement thresholds and larger motor maps indicative of higher excitation/inhibition compared to C57BL/6J (B6) controls, and that the KD reversed both these abnormalities. Collectively, our results afford a greater understanding of cortical excitation/inhibition balance in ASD and may help expedite the development of therapeutic approaches aimed at improving functional outcomes in this disorder.

Seizure control by decanoic acid through direct AMPA receptor inhibition

See Rogawski (doi:10.1093/awv369) for a scientific commentary on this article. 

The medium chain triglyceride ketogenic diet is an established treatment for drug-resistant epilepsy that increases plasma levels of decanoic acid and ketones. Recently, decanoic acid has been shown to provide seizure control in vivo, yet its mechanism of action remains unclear. Here we show that decanoic acid, but not the ketones β-hydroxybutryate or acetone, shows antiseizure activity in two acute ex vivo rat hippocampal slice models of epileptiform activity. To search for a mechanism of decanoic acid, we show it has a strong inhibitory effect on excitatory, but not inhibitory, neurotransmission in hippocampal slices. Using heterologous expression of excitatory ionotropic glutamate receptor AMPA subunits in Xenopus oocytes, we show that this effect is through direct AMPA receptor inhibition, a target shared by a recently introduced epilepsy treatment perampanel. Decanoic acid acts as a non-competitive antagonist at therapeutically relevant concentrations, in a voltage- and subunit-dependent manner, and this is sufficient to explain its antiseizure effects. This inhibitory effect is likely to be caused by binding to sites on the M3 helix of the AMPA-GluA2 transmembrane domain; independent from the binding site of perampanel. Together our results indicate that the direct inhibition of excitatory neurotransmission by decanoic acid in the brain contributes to the anti-convulsant effect of the medium chain triglyceride ketogenic diet.

A randomised trial of a medium-chain TAG diet as treatment for dogs with idiopathic epilepsy

Despite appropriate antiepileptic drug treatment, approximately one-third of humans and dogs with epilepsy continue experiencing seizures, emphasising the importance for new treatment strategies to improve the quality of life of people or dogs with epilepsy. A 6-month prospective, randomised, double-blinded, placebo-controlled cross-over dietary trial was designed to compare a ketogenic medium-chain TAG diet (MCTD) with a standardised placebo diet in chronically antiepileptic drug-treated dogs with idiopathic epilepsy. Dogs were fed either MCTD or placebo diet for 3 months followed by a subsequent respective switch of diet for a further 3 months. Seizure frequency, clinical and laboratory data were collected and evaluated for twenty-one dogs completing the study. Seizure frequency was significantly lower when dogs were fed the MCTD (2·31/month, 0-9·89/month) in comparison with the placebo diet (2·67/month, 0·33-22·92/month, P=0·020); three dogs achieved seizure freedom, seven additional dogs had ≥50 % reduction in seizure frequency, five had an overall <50 % reduction in seizures (38·87 %, 35·68-43·27 %) and six showed no response. Seizure day frequency were also significantly lower when dogs were fed the MCTD (1·63/month, 0-7·58/month) in comparison with the placebo diet (1·69/month, 0·33-13·82/month, P=0·022). Consumption of the MCTD also resulted in significant elevation of blood β-hydroxybutyrate concentrations in comparison with placebo diet (0·071 (sd 0·035) v. 0·053 (sd 0·028) mmol/l, P=0·028). There were no significant changes in serum concentrations of glucose (P=0·903), phenobarbital (P=0·422), potassium bromide (P=0·404) and weight (P=0·300) between diet groups. In conclusion, the data show antiepileptic properties associated with ketogenic diets and provide evidence for the efficacy of the MCTD used in this study as a therapeutic option for epilepsy treatment.

β-Hydroxybutyrate attenuates NMDA-induced spasms in rats with evidence of neuronal stabilization on MR spectroscopy

BACKGROUND

Infantile spasms (IS) is a devastating epileptic encephalopathy. The ketogenic diet (KD) has been successfully used as a treatment for IS. This study was designed to test whether beta-hydroxybutyrate (BHB), a major metabolite of the KD, is effective in an animal model of IS.

METHODS

Pregnant rats received betamethasone on gestational day 15. The offspring received either single [30min prior to NMDA-triggered spasms on postnatal day (P) 15] or prolonged (three per day from P12 to P15) i.p. BHB. An additional experiment used repeated bouts of spasms on P12, P13, and P15 with randomized prolonged BHB treatment initiated after the first spasms. We determined the latency to onset of spasms and the number of spasms after the NMDA injection on P15. The rats that received randomized BHB treatment were also monitored with open field, sociability, and fear-conditioning tests and underwent in vivo (1)H MR imaging on a 9.4T MR system after NMDA-induced spasms. The acquired (1)H MR spectra were quantified using LC model.

RESULTS

Single-dose BHB pretreatment had no effect on spasms. In contrast, prolonged pretreatment with BHB significantly delayed the onset and decreased the frequency of spasms. In addition, randomized prolonged BHB treatment resulted in a significant reduction in number of spasms at P15. BHB treatment had no significant effect on motor activities, but significantly decreased the interactions with strangers and increased the contextual memory. On MR spectroscopic analysis of randomized prolonged BHB-treated rats at 24h after the cluster of spasms, the elevation of GABA, glutamine, glutamate, total creatine, macromolecule-plus lipids, and N-acetylaspartate levels after spasms were significantly attenuated by randomized BHB treatment (p<0.05).

SIGNIFICANCE

Prolonged administration of BHB directly suppresses development of spasms in a rat model of IS with acute stabilization of brain metabolites. Additionally, BHB appears to decrease the interests to other rats and improve memory responses.

Anticonvulsant properties of an oral ketone ester in a pentylenetetrazole-model of seizure

The ketogenic diet is known to have an anti-epileptic effect; in fact it is currently used to treat drug resistant epilepsies. The efficacy of this diet is thought to be correlated to the elevation of blood ketone bodies. Because of problems with compliance to this diet, there is an interest in evaluating alternative pharmacological treatments that can have anti-seizure effects by elevating ketone bodies. In the present experiment, an orally administered synthetic ketone ester (R,S - 1,3-butanediol acetoacetate diester, or BD-AcAc2) was evaluated for its anti-seizure efficacy in a rat model. The threshold for seizure induction with progressive intravenous infusion of pentylenetrazole (PTZ) was evaluated in anesthetized Wistar rats two hours after a single 1 ml intragastric administration of BD-AcAc2 (i.e. 4 g/kg b.w., treated group) or water (control group). After correction for the dose of anesthetic, the results showed that the administration of BD-AcAc2 induced an elevation of the PTZ threshold (140 ± 11 mg/kg for the treated group, 122 ± 6 mg/kg for the control group), along with an increased level of blood β-hydroxybutyrate (2.7 ± 0.3mM for the treated group, 1.4 ± 0.1mM for the control group). This result suggests that ketone esters may pave the road towards the establishment of a "ketogenic diet in a pill".

Evidence to support mitochondrial neuroprotection, in severe traumatic brain injury

Traumatic brain injury (TBI) is still the leading cause of disability in young adults worldwide. The major mechanisms - diffuse axonal injury, cerebral contusion, ischemic neurological damage, and intracranial hematomas have all been shown to be associated with mitochondrial dysfunction in some form. Mitochondrial dysfunction in TBI patients is an active area of research, and attempts to manipulate neuronal/astrocytic metabolism to improve outcomes have been met with limited translational success. Previously, several preclinical and clinical studies on TBI induced mitochondrial dysfunction have focused on opening of the mitochondrial permeability transition pore (PTP), consequent neurodegeneration and attempts to mitigate this degeneration with cyclosporine A (CsA) or analogous drugs, and have been unsuccessful. Recent insights into normal mitochondrial dynamics and into diseases such as inherited mitochondrial neuropathies, sepsis and organ failure could provide novel opportunities to develop mitochondria-based neuroprotective treatments that could improve severe TBI outcomes. This review summarizes those aspects of mitochondrial dysfunction underlying TBI pathology with special attention to models of penetrating traumatic brain injury, an epidemic in modern American society.

Ketogenic diet in neuromuscular and neurodegenerative diseases

An increasing number of data demonstrate the utility of ketogenic diets in a variety of metabolic diseases as obesity, metabolic syndrome, and diabetes. In regard to neurological disorders, ketogenic diet is recognized as an effective treatment for pharmacoresistant epilepsy but emerging data suggests that ketogenic diet could be also useful in amyotrophic lateral sclerosis, Alzheimer, Parkinson's disease, and some mitochondriopathies. Although these diseases have different pathogenesis and features, there are some common mechanisms that could explain the effects of ketogenic diets. These mechanisms are to provide an efficient source of energy for the treatment of certain types of neurodegenerative diseases characterized by focal brain hypometabolism; to decrease the oxidative damage associated with various kinds of metabolic stress; to increase the mitochondrial biogenesis pathways; and to take advantage of the capacity of ketones to bypass the defect in complex I activity implicated in some neurological diseases. These mechanisms will be discussed in this review.

Influence of a ketogenic diet, fish-oil, and calorie restriction on plasma metabolites and lipids in C57BL/6J mice

BACKGROUND

Diet therapies including calorie restriction, ketogenic diets, and fish-oil supplementation have been used to improve health and to treat a variety of neurological and non-neurological diseases.

METHODS

We investigated the effects of three diets on circulating plasma metabolites (glucose and β-hydroxybutyrate), hormones (insulin and adiponectin), and lipids over a 32-day period in C57BL/6J mice. The diets evaluated included a standard rodent diet (SD), a ketogenic diet (KD), and a standard rodent diet supplemented with fish-oil (FO). Each diet was administered in either unrestricted (UR) or restricted (R) amounts to reduce body weight by 20%.

RESULTS

The KD-UR increased body weight and glucose levels and promoted a hyperlipidemic profile, whereas the FO-UR decreased body weight and glucose levels and promoted a normolipidemic profile, compared to the SD-UR. When administered in restricted amounts, all three diets produced a similar plasma metabolite profile, which included decreased glucose levels and a normolipidemic profile. Linear regression analysis showed that circulating glucose most strongly predicted body weight and triglyceride levels, whereas calorie intake moderately predicted glucose levels and strongly predicted ketone body levels.

CONCLUSIONS

These results suggest that biomarkers of health can be improved when diets are consumed in restricted amounts, regardless of macronutrient composition.

The ketogenic diet component decanoic acid increases mitochondrial citrate synthase and complex I activity in neuronal cells

The Ketogenic diet (KD) is an effective treatment with regards to treating pharmaco-resistant epilepsy. However, there are difficulties around compliance and tolerability. Consequently, there is a need for refined/simpler formulations that could replicate the efficacy of the KD. One of the proposed hypotheses is that the KD increases cellular mitochondrial content which results in elevation of the seizure threshold. Here, we have focussed on the medium-chain triglyceride form of the diet and the observation that plasma octanoic acid (C8) and decanoic acid (C10) levels are elevated in patients on the medium-chain triglyceride KD. Using a neuronal cell line (SH-SY5Y), we demonstrated that 250-μM C10, but not C8, caused, over a 6-day period, a marked increase in the mitochondrial enzyme, citrate synthase along with complex I activity and catalase activity. Increased mitochondrial number was also indicated by electron microscopy. C10 is a reported peroxisome proliferator activator receptor γ agonist, and the use of a peroxisome proliferator activator receptor γ antagonist was shown to prevent the C10-mediated increase in mitochondrial content and catalase. C10 may mimic the mitochondrial proliferation associated with the KD and raises the possibility that formulations based on this fatty acid could replace a more complex diet. We propose that decanoic acid (C10) results in increased mitochondrial number. Our data suggest that this may occur via the activation of the PPARγ receptor and its target genes involved in mitochondrial biogenesis. This finding could be of significant benefit to epilepsy patients who are currently on a strict ketogenic diet. Evidence that C10 on its own can modulate mitochondrial number raises the possibility that a simplified and less stringent C10-based diet could be developed.

Deep sequencing reveals increased DNA methylation in chronic rat epilepsy

Epilepsy is a frequent neurological disorder, although onset and progression of seizures remain difficult to predict in affected patients, irrespective of their epileptogenic condition. Previous studies in animal models as well as human epileptic brain tissue revealed a remarkably diverse pattern of gene expression implicating epigenetic changes to contribute to disease progression. Here we mapped for the first time global DNA methylation patterns in chronic epileptic rats and controls. Using methyl-CpG capture associated with massive parallel sequencing (Methyl-Seq) we report the genomic methylation signature of the chronic epileptic state. We observed a predominant increase, rather than loss of DNA methylation in chronic rat epilepsy. Aberrant methylation patterns were inversely correlated with gene expression changes using mRNA sequencing from same animals and tissue specimens. Administration of a ketogenic, high-fat, low-carbohydrate diet attenuated seizure progression and ameliorated DNA methylation mediated changes in gene expression. This is the first report of unsupervised clustering of an epigenetic mark being used in epilepsy research to separate epileptic from non-epileptic animals as well as from animals receiving anti-convulsive dietary treatment. We further discuss the potential impact of epigenetic changes as a pathogenic mechanism of epileptogenesis.

Therapeutic ketosis with ketone ester delays central nervous system oxygen toxicity seizures in rats

Central nervous system oxygen toxicity (CNS-OT) seizures occur with little or no warning, and no effective mitigation strategy has been identified. Ketogenic diets (KD) elevate blood ketones and have successfully treated drug-resistant epilepsy. We hypothesized that a ketone ester given orally as R,S-1,3-butanediol acetoacetate diester (BD-AcAc(2)) would delay CNS-OT seizures in rats breathing hyperbaric oxygen (HBO(2)). Adult male rats (n = 60) were implanted with radiotelemetry units to measure electroencephalogram (EEG). One week postsurgery, rats were administered a single oral dose of BD-AcAc(2), 1,3-butanediol (BD), or water 30 min before being placed into a hyperbaric chamber and pressurized to 5 atmospheres absolute (ATA) O2. Latency to seizure (LS) was measured from the time maximum pressure was reached until the onset of increased EEG activity and tonic-clonic contractions. Blood was drawn at room pressure from an arterial catheter in an additional 18 animals that were administered the same compounds, and levels of glucose, pH, Po(2), Pco(2), β-hydroxybutyrate (BHB), acetoacetate (AcAc), and acetone were analyzed. BD-AcAc(2) caused a rapid (30 min) and sustained (>4 h) elevation of BHB (>3 mM) and AcAc (>3 mM), which exceeded values reported with a KD or starvation. BD-AcAc(2) increased LS by 574 ± 116% compared with control (water) and was due to the effect of AcAc and acetone but not BHB. BD produced ketosis in rats by elevating BHB (>5 mM), but AcAc and acetone remained low or undetectable. BD did not increase LS. In conclusion, acute oral administration of BD-AcAc(2) produced sustained ketosis and significantly delayed CNS-OT seizures by elevating AcAc and acetone.

Ketogenic diets and thermal pain: dissociation of hypoalgesia, elevated ketones, and lowered glucose in rats

Ketogenic diets (KDs) are high-fat, low-carbohydrate formulations effective in treating medically refractory epilepsy, and recently we demonstrated lowered sensitivity to thermal pain in rats fed a KD for 3 to 4 weeks. Regarding anticonvulsant and hypoalgesic mechanisms, theories are divided as to direct effects of increased ketones and/or decreased glucose, metabolic hallmarks of these diets. To address this point, we characterized the time course of KD-induced thermal hypoalgesia, ketosis, and lowered glucose in young male rats fed ad libitum on normal chow or KDs. A strict 6.6:1 (fat:[carbohydrates + protein], by weight) KD increased blood ketones and reduced blood glucose by 2 days of feeding, but thermal hypoalgesia did not appear until 10 days. Thus, ketosis and decreased glucose are not sufficient for hypoalgesia. After feeding a 6.6:1 KD for 19 days, decreased thermal pain sensitivity and changes in blood chemistry reversed 1 day after return to normal chow. Effects were consistent between 2 different diet formulations: a more moderate and clinically relevant KD formula (3.0:1) produced hypoalgesia and similar changes in blood chemistry as the 6.6:1 diet, thus increasing translational potential. Furthermore, feeding the 3.0:1 diet throughout an extended protocol (10-11 weeks) revealed that significant hypoalgesia and increased ketones persisted whereas low glucose did not, demonstrating that KD-induced hypoalgesia does not depend on reduced glucose. In separate experiments we determined that effects on thermal pain responses were not secondary to motor or cognitive changes. Together, these findings dissociate diet-related changes in nociception from direct actions of elevated ketones or decreased glucose, and suggest mechanisms with a slower onset in this paradigm. Overall, our data indicate that metabolic approaches can relieve pain.

PERSPECTIVE

Chronic pain is a common and debilitating condition. We show that a KD, a high-fat, very low carbohydrate diet well known for treating epilepsy, lowers sensitivity to thermal pain in rats. This reduced pain is not temporally correlated with hallmark diet-induced changes in blood glucose and ketones.

Seizure control by ketogenic diet-associated medium chain fatty acids

The medium chain triglyceride (MCT) ketogenic diet is used extensively for treating refractory childhood epilepsy. This diet increases the plasma levels of medium straight chain fatty acids. A role for these and related fatty acids in seizure control has not been established. We compared the potency of an established epilepsy treatment, Valproate (VPA), with a range of MCT diet-associated fatty acids (and related branched compounds), using in vitro seizure and in vivo epilepsy models, and assessed side effect potential in vitro for one aspect of teratogenicity, for liver toxicology and in vivo for sedation, and for a neuroprotective effect. We identify specific medium chain fatty acids (both prescribed in the MCT diet, and related compounds branched on the fourth carbon) that provide significantly enhanced in vitro seizure control compared to VPA. The activity of these compounds on seizure control is independent of histone deacetylase inhibitory activity (associated with the teratogenicity of VPA), and does not correlate with liver cell toxicity. In vivo, these compounds were more potent in epilepsy control (perforant pathway stimulation induced status epilepticus), showed less sedation and enhanced neuroprotection compared to VPA. Our data therefore implicates medium chain fatty acids in the mechanism of the MCT ketogenic diet, and highlights a related new family of compounds that are more potent than VPA in seizure control with a reduced potential for side effects.

This article is part of the Special Issue entitled ‘New Targets and Approaches to the Treatment of Epilepsy’.

Diet composition exacerbates or attenuates soman toxicity in rats: implied metabolic control of nerve agent toxicity

To evaluate the role of diet composition on nerve agent toxicity, rats were fed four distinct diets ad libitum for 28 d prior to challenge with 110 μg/kg (1.0 LD(50), sc) soman. The four diets used were a standard rodent diet, a choline-enriched diet, a glucose-enriched diet, and a ketogenic diet. Body weight was recorded throughout the study. Toxic signs and survival were evaluated at key times for up to 72 h following soman exposure. Additionally, acquisition of discriminated shuttlebox avoidance performance was characterized beginning 24h after soman challenge and across the next 8 d (six behavioral sessions). Prior to exposure, body weight was highest in the standard diet group and lowest in the ketogenic diet group. Upon exposure, differences in soman toxicity as a function of diet became apparent within the first hour, with mortality in the glucose-enriched diet group reaching 80% and exceeding all other groups (in which mortality ranged from 0 to 6%). At 72 h after exposure, mortality was 100% in the glucose-enriched diet group, and survival approximated 50% in the standard and choline-enriched diet groups, but equaled 87% in the ketogenic diet group. Body weight loss was significantly reduced in the ketogenic and choline-enriched diet groups, relative to the standard diet group. At 1 and 4h after exposure, rats in the ketogenic diet group had significantly lower toxic sign scores than all other groups. The ketogenic diet group performed significantly better than the standard diet group on two measures of active avoidance performance. The exacerbated soman toxicity observed in the glucose-enriched diet group coupled with the attenuated soman toxicity observed in the ketogenic diet group implicates glucose availability in the toxic effects of soman. This increased glucose availability may enhance acetylcholine synthesis and/or utilization, thereby exacerbating peripheral and central soman toxicity.

Purines and the Anti-Epileptic Actions of Ketogenic Diets

Ketogenic diets are high in fat and low in carbohydrates and represent a well-established and effective treatment alternative to anti-epileptic drugs. Ketogenic diets are used for the management of a variety of difficult-to-treat or intractable seizure disorders, especially pediatric refractory epilepsy. However, it has been shown that this dietary therapy can reduce seizures in people of all ages, and ketogenic diets are being applied to other prevalent medical conditions such as diabetes. Although used effectively to treat epilepsy for nearly 90 years, the mechanism(s) by which ketogenic diets work to reduce seizures remain ill-understood. One mechanism receiving increased attention is based on findings that ketogenic diets increase the brain energy molecule ATP, and may also increase the levels and actions of the related endogenous inhibitory neuromodulator adenosine. ATP and adenosine have both been identified as important modulators of seizures; seizures increase the actions of these purines, these purines regulate epileptic activity in brain, adenosine receptor antagonists are pro-convulsant, and adenosinergic mechanisms have been implicated previously in the actions of approved anti-epileptic therapeutics. Here we will review recent literature and describe findings that shed light on mechanistic relationships between ketogenic diets and the purines ATP and adenosine. These emerging mechanisms hold great promise for the effective therapeutic management of epileptic seizures and other neurological conditions.